I've got both the Vintage 6 hole Callaham (lefty), and the Am Std Strat upgrade (lefty as well).
The Am Std Strat upgrade has the same heavy-arse cold-rolled steel trem block... the saddles are, of course
the same material as the V6hole, but smaller in width due to the AmStd Strat trem spacing.
As well, they are the stamped variety just like the V6hole (a major reason I went with the
upgrade - hate the pingy treble tone of the Fender Am Std Strat pot-metal block saddles).
And of course, I'm using the original Fender Am Std 2-point trem plate with the Callaham stuff...
everything fits easily.
My Am Std beater Strat is still waiting for parts, so I can't say how it is... yet.
But my Warmoth strat with the vintage Callaham trem punches other strats in the face, knees them in
the groin and then steals their lunch money; leaving them cryin' for momma. :icon_biggrin:
Tuning stability is great (not perfect of course) comparatively as well.
As far as springs, that's personal preference; how much tension do you want when
bending strings? etc - I use 3 springs on my V6hole.
For the floating part, I have mine lifting off the body by a few 16ths of an inch... so I have a wee bit of pull up for squealies
when they decide to make themselves known.
Addendum: BTW, the "virtual pop in arm" is schweet. There's a bushing in the block that holds the arm in place... and a few threads
on the tip of the arm to keep it in there. Totally touch-sensitive with the arm and zero slop - none.